1936, derogatory slang form of pink (n., adj.), used of people whose social or political views "have a tendency toward 'red;' " a metaphor that had existed since at least 1837.
n. a communist. (Popular during the 1950s.) : Get out of here, you pinko!
mod. having communist tendencies; in the manner of a communist. : Get that pinko jerk out of here!
Dictionary of American Slang and Colloquial Expressions by Richard A. Spears.Fourth Edition. Copyright 2007. Published by McGraw Hill.
Cite This Source